Answer:
Always in you, sometimes on you. If I surround you, I can kill you. What am I?
I will disappear every time you say my name. What am I?
I fly yet I have no wings. I cry yet I have no eyes. Darkness follows me. Lower light I never see.
What's made of water but if you put it into water it will die?
I am tomorrow's yesterday and yesterday's tomorrow. What am I?
No matter how little or how much you use me, you change me every month.